An experiment is proposed to investigate the psychophysiological functions of positive emotions, which are suggested to be quite distinct from those associated with negative emotions. Emotion researchers generally agree that negative emotions function to prepare individuals for specific, ancestrally adaptive actions by recruiting heightened physiological activation. This link between emotions and specific action tendencies is often taken as definitional for all emotions, even though supportive data from positive emotions is lacking. An alternative model, specific to the positive emotions, is offered to account for this gap in the empirical literature. This model proposes that positive emotions function to quell or undo the action tendencies and physiological activation generated by specific negative emotions. A laboratory-based experiment is proposed to test the generality this "undoing" model of positive emotions. Cardiovascular activity is monitored with continuous measures of heart rate, peripheral vasoconstriction and blood pressure. The experimental paradigm involves eliciting negative emotion with attendant cardiovascular activation in all subjects, then using a between-subjects design to test whether stimuli that elicit positive emotions speed recovery from heightened cardiovascular arousal faster than do comparable stimuli that do not elicit positive emotion. The proposed experiment tests the generality of the undoing function of positive emotion by using (a) multiple negative emotions to generate the initial cardiovascular activation (anger, disgust); (b)multiple means of eliciting these initial negative emotions (emotional memories, emotionally-evocative films); and (c) multiple stimuli to elicit positive emotions (films that elicit amusement, contentment). This research is motivated by the empirical evidence that implicates the cardiovascular reactivity associated with negative emotions in the etiology of cardiovascular diseases. Empirical evidence regarding the functions of positive emotions can inform prevention and treatment regimens designed to reduce risk for cardiovascular disease and promote physical and psychological health and well-being.